1. Design content
Consists of STC89C52 single-chip microcomputer + DS18B20 temperature sensor + LCD1602 LCD display + 5V relay + 5V fan + heating film + button + buzzer + power supply
Specific functions: 1. LCD1602 LCD displays the measured temperature in real time;
2. Temperature alarm can be set Upper and lower limit values; key functions: plus key, minus key, setting key
3. Sound and light alarm will start when the upper and lower alarm limits are exceeded;
4. The measured temperature exceeds the upper limit, the relay is closed, and the electric fan starts to work ; The measured temperature is lower than the lower limit, the relay is closed, and the heating film starts to work.
2. Hardware design plan
The whole system takes STC89C52 single-chip microcomputer as the core device, and cooperates with the resistance capacitor crystal oscillator and other devices to form the smallest single-chip microcomputer system. The other modules are developed around the smallest system of the microcontroller. Among them, the sensor adopts DS18B20, which is responsible for collecting temperature data and sending it to the microcontroller. The display device uses a 4-digit common cathode digital tube to display the detected temperature value. The key module is mainly for setting the alarm value. The alarm module adopts the buzzer + LED mode. If the alarm range is exceeded, it will give an audible and visual alarm. At the same time, there are also heating and cooling devices to keep the temperature constant within a range.
3. Software design ideas
The software design of this system first initializes the timer, and uses the timer to realize the dynamic scanning of the digital tube. Then it enters an infinite loop, the infinite loop executes the following content: 1. Read the current temperature value; 2. Display the detected temperature value; 3. Determine whether the detected temperature exceeds the set upper and lower limits, if yes, start the sound Light alarm and analog constant temperature device; 4. Delay and scan the keys. If the key is pressed, it will enter the state of setting the upper and lower temperature limits.
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